10,990 research outputs found
Experimental study of acoustic displays of flight parameters in a simulated aerospace vehicle
Evaluating acoustic displays of target location in target detection and of flight parameters in simulated aerospace vehicle
Development of the PsAQoL: a quality of life instrument specific to psoriatic arthritis
Background: Patient reported outcome measures used in studies of psoriatic arthritis (PsA) have been
found to be inadequate for determining the impact of the disease from the patient’s perspective.
Objective: To produce the PsAQoL, a PsA-specific quality of life (QoL) instrument, employing the needs
based model of QoL that would be relevant and acceptable to respondents, valid, and reliable.
Methods: Content was derived from qualitative interviews conducted with patients with PsA. Face and
content validity were assessed by field test interviews with a new sample of patients with PsA. A postal
survey was conducted to improve the scaling properties of the new measure. Finally, a test-retest postal
survey was used to identify the final measure and to test its scaling properties, reliability, internal
consistency, and validity.
Results: Analysis of the qualitative interview transcripts identified a 51 item questionnaire. Field test
interviews confirmed the acceptability and relevance of the measure. Analysis of data from the first postal
survey (n = 94) reduced the questionnaire to 35 items. Rasch analysis of data from the test-retest survey
(n = 286) identified a 20 item version of the PsAQoL with good item fit. This version had excellent internal
consistency (a = 0.91), test-retest reliability (0.89), and validity.
Conclusions: The PsAQoL is a valuable tool for assessing the impact of interventions for PsA in clinical
studies and trials. It is well accepted by patients, taking about three minutes to complete, is easy to
administer, and has excellent scaling and psychometric properties
On the Validity of the Tomonaga Luttinger Liquid Relations for the One-dimensional Holstein Model
For the one-dimensional Holstein model, we show that the relations among the
scaling exponents of various correlation functions of the Tomonaga Luttinger
liquid (LL), while valid in the thermodynamic limit, are significantly modified
by finite size corrections. We obtain analytical expressions for these
corrections and find that they decrease very slowly with increasing system
size. The interpretation of numerical data on finite size lattices in terms of
LL theory must therefore take these corrections into account. As an important
example, we re-examine the proposed metallic phase of the zero-temperature,
half-filled one-dimensional Holstein model without employing the LL relations.
In particular, using quantum Monte Carlo calculations, we study the competition
between the singlet pairing and charge ordering. Our results do not support the
existence of a dominant singlet pairing state.Comment: 7 page
Evidence of Electron Fractionalization from Photoemission Spectra in the High Temperature Superconductors
In the normal state of the high temperature superconductors
Bi_2Sr_2CaCu_2O_{8+delta} and La_{2-x}Sr_{x}CuO_4, and in the related ``stripe
ordered'' material La_1.25Nd_0.6Sr_0.15CuO_4, there is sharp structure in the
measured single hole spectral function A(k,w) considered as a function of k at
fixed small binding energy w. At the same time, as a function of w at fixed k
on much of the putative Fermi surface, any structure in A(k,w), other than the
Fermi cutoff, is very broad. This is characteristic of the situation in which
there are no stable excitations with the quantum numbers of the electron, as is
the case in the one dimensional electron gas.Comment: Published versio
Classical Phase Fluctuations in Incommensurate Peierls Chains
In the pseudogap regime of one-dimensional incommensurate Peierls systems,
fluctuations of the phase of the order parameter prohibit the emergence of
long-range order and generate a finite correlation length. For classical phase
fluctuations, we present exact results for the average electronic density of
states, the mean localization length, the electronic specific heat and the spin
susceptibility at low temperatures. Our results for the susceptibility give a
good fit to experimental data.Comment: 4 Revtex pages, 4 figures, submitted to Phys. Rev. Let
Luther-Emery Stripes, RVB Spin Liquid Background and High Tc Superconductivity
The stripe phase in high Tc cuprates is modeled as a single stripe coupled to
the RVB spin liquid background by the single particle hopping process. In
normal state, the strong pairing correlation inherent in RVB state is thus
transfered into the Luttinger stripe and drives it toward spin-gap formation
described by Luther-Emery Model. The establishment of global phase coherence in
superconducting state contributes to a more relevant coupling to
Luther-Emery Stripe and leads to gap opening in both spin and charge sectors.
Physical consequences of the present picture are discussed, and emphasis is put
on the unification of different energy scales relevant to cuprates, and good
agreement is found with the available experimental results, especially in
ARPES.Comment: 4 pages, RevTe
Unusual metallic phase in a chain of strongly interacting particles
We consider a one-dimensional lattice model with the nearest-neighbor
interaction and the next-nearest neighbor interaction with filling
factor 1/2 at zero temperature. The particles are assumed to be spinless
fermions or hard-core bosons. Using very simple assumptions we are able to
predict the basic structure of the insulator-metal phase diagram for this
model. Computations of the flux sensitivity support the main features of the
proposed diagram and show that the system maintains metallic properties at
arbitrarily large values of and along the line ,
where is the hopping amplitude, and . We think that close
to this line the system is a ``weak'' metal in a sense that the flux
sensitivity decreases with the size of the system not exponentially but as
with .Comment: To appear in J. Phys. C; 9 revtex preprint pages + 4 ps figures,
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On Emery-Kivelson line and universality of Wilson ratio of spin anisotropic Kondo model
Yuval-Anderson's scaling analysis and Affleck-Ludwig's Conformal Field Theory
approach are applied to the channel {\em spin anisotropic} Kondo model.
Detailed comparisons with the available Emery-Kivelson's Abelian Bosonization
approaches are made. It is shown that the EK line exists for any , although
it can be mapped to free fermions only when or . The Wilson ratio is
universal if or , but {\em not} universal if . The leading low
temperature correction to the electron resistivity is {\em not} affected by the
spin anisotropy for {\em any} . A new universal ratio for is proposed
to compare with experiments.Comment: 12 pages, REVTEX, no figures, to appear in Phys. Rev. Lett
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